Ion channels are membrane proteins that allow the selective movement of charged molecules through cellular membranes. Many disease states, such as cystic fibrosis, muscular dystrophies, hypertension, and cardiac arrhythmias are caused by ion channel pathologies. Ion channels have been identified by the drug discovery community as excellent targets for therapeutic intervention but because of the technical hurdles involved in developing quality, high-throughput functional ion channel assays, the development of "ion channel drugs" has been disappointing. Photoswitch Biosciences has developed technology, which allows attaching small nanomachines to ion channels enabling rapid and reversible control of these proteins by light. The three Specific Aims of the proposed project are: (1) optimization of the dynamic range of changes in membrane potential driven by photoswitched channels in mammalian cell lines, (2) optimization of cell line, photoswitched channel and membrane potential range to assay several voltage-gated ion channel targets using electrophysiological detection, and (3) conversion of the assay to an all-optical readout by substituting indicator dyes for electrophysiology detection. The first commercial products to be developed will be all-optical ion channel assays and instruments for high- throughput ion channel drug discovery. The use of all-optical technology for ion channel assays has several advantages over existing techniques: (1) Elimination of liquid additions for channel activation, (2) Highly scalable for high-throughput ion channel drug discovery, (3) Price per datapoint is at least 100X less than automated electrophysiology, (4) Channel activation is almost 100X faster than KCl addition. The most important benefit of this new ion channel assay technology is the ability to rapidly and reliably control membrane potential. This control of membrane potential allows for the development of scalable high-throughput state-dependent assays, which is impossible with current technology. This breakthrough technology will finally allow the full exploitation of ion channels as drug targets. PUBLIC HEALTH RELEVANCE: Many diseases involve problems with the functioning of membrane proteins called ion channels. These proteins are responsible for proper operation of the nervous system, the muscles, and virtually all other physiological events. Drugs that affect ion channel behavior have been developed for a variety of diseases, including heart problems, cystic fibrosis, and other diseases. Ion channels are difficult to study and, because of this, drugs directed at ion channels have been difficult to find. Photoswitch Biosciences proposes to develop methods to increase the ability to study ion channels, and, thus, to increase the number of ion channel drugs.